The present invention is in the field of data processing, and more particularly relates to linear spatial filter systems.
Spatial filters are known in the art to be very effective in the restoration and enhancement of digitized images. Moreover, two dimensional linear matched filtering as a technique has been recognized as being particularly effective in the detection and acquisition of targets in a high clutter environment.
In the particular area of target acquisition, high resolution, high sensitivity infrared images may be obtained for a scene in which the target is sought. Conventionally, these scenes are acquired using mercury-cadmium-telluride (HgCdTe) detectors which are assembled into long linear arrays. The linear arrays are generally mounted in an evacuated dewar containing liquid nitrogen at 77 degrees Kelvin.
In order to obtain the infrared scene information from the arrays of detectors, the relatively long linear arrays are scanned in the direction perpendicular to their long dimension. The scan data may then be filtered in real time using, for example, a multitapped CCD delay line with weighted summing devices coupled to desired combinations of the taps. See J. T. Carlo and J. E. Hall, "Spatial Filtering Using 3.times.3 Kernal Convolutions", SPIE, Vol. 178, Smart Sensors (1979) pp. 154-161.
However, conventional spatial filtering techniques require a relatively large number of data transfers to generate the convolution. Furthermore, those are characterized by relatively strict limitations on the speed at which these transfers must take place. Generally, in the prior art, the data-to-be-filtered is brought out of the dewar with one serial CCD array, and then is fed into a much longer serial delay line. For an mxn filter, n-1 lines of data must be stored. Where there are r detector elements in the vertical detector array, each data sample undergoes (n-1)r+m shifts at a shift rate of r/T.sub.d, where T.sub.d is the detector dwell time. However, due to the long delay lines, the data tends to degrade (or smear) and this smearing gets worse as the delay line gets longer and the transfer rate increases.
It is an object of the present invention to provide an improved spatial filter system.
It is another object to provide a spatial filter system for use in conjunction with detectors within a dewar.